Thanks everyone, I couldnt get the serger to roll hem nicely, the stitching just kept pulling away as I was sewing, snagging up under the serger foot, and then getting tangled in the mechanism. I ended up using the sewing machine roll foot with a small zig zag - which was no problem. Can understand how I managed to make such a mess or the serger rolled hem, ive never really got on with it though :-)